An objective of the present invention is to satisfy a need for a practical and efficient machine for reconditioning the vertical walls of paper pulp digesters in situ, such digesters ranging in size from eight and one-half to twenty-four feet in diameter and from thirty to more than two hundred feet in height. The vertical walls of digesters periodically require repair by weld deposition, and air carbon arc gouging may be required in preparation for repair by welding. While the invention is ideally suited for the above usage, it also finds utility in many other similar applications for the repair of interior and exterior surfaces of curved and flat vertical walls.
In accordance with the invention, the required digester side wall reconditioning operations are carried out by a portable table-mounted machine which can be placed at a required location inside of a massive digester and locked in place. The machine is operated by state-of-the-art controls, systematically causing electric arc welding nozzles or an air carbon arc torch to traverse the cylindrical side wall of a digester horizontally, while automatically maintaining proper welding nozzle or gouging torch alignment with the digester side wall, and also maintaining a constant speed of traverse of the welding nozzles or gouging torch across the vertical side wall. The machine aso has means to drive welding nozzles and a gouging torch upwardly or downwardly vertically on a positioning assembly carried by the horizontally swingable carriage arm of the machine. Welding material from a supply source on the carriage arm is delivered by a drive assembly also on the carriage arm to the adjustable welding nozzle or nozzles.
The reconditioning machine embodying the present invention obviates the need for mounting the machine on or attaching it to the vertical wall undergoing repair in accordance with some prior art practice. The difficulty of such practice resides in the time and labor required to mount and align the system, and if welded to the vertical wall, the additional time and labor required to remove the machine and repair the mounting areas.
The machine in accordance with the present invention is self-standing and securely lockable in the position of use. It rests on a stable platform within the digester and the vertical axis center of rotation of the machine carriage arm need not coincide with the center of the digester. When required, the machine can also be supported at the proper elevation to repair the exterior of the side wall of a digester or for a similar application.
Other features and advantages of the invention will become apparent to those skilled in the art during the course of the following description.